1. Technical Field of the Invention
The present invention relates generally to the mobile telecommunications field; and, more particularly, to a method and system for protecting the integrity of the interface between a mobile device, and a “smart” card provided in the mobile device.
2. Description of Related Art
In the mobile telecommunications field, a smart card provides the mechanism by which a Mobile Station (MS), such as a mobile telephone or other mobile device, can be “locked” to a particular telecommunications network. The smart card is mounted in a mobile device and provides a network subscriber with authorization to use the mobile device in the network; and, in addition, provides the network operator with the ability to control the manner in which the mobile device is used in the network.
In GSM (Global System for Mobile Communications), the smart card is generally referred to as a SIM (Subscriber Information Module) card; and in the following description, reference will primarily be made to a SIM card used in GSM. It should be understood, however, that the present invention is not limited to SIM cards or to GSM, but is intended to cover other smart cards used in other wireless telecommunications systems such as, for example, the UICC (Universal Integrated Circuit Card) card that is used in UMTS (Universal Mobile Telecommunications System).
In GSM, the SIM card is the main secure carrier of private/secret (key) information to authorize network access to and to provide, via SAT (SIM Application Toolkit), control over a mobile device. In particular, the SIM card carries network parameters (in, for example, so-called GID fields) that control the SIM lock functionality by which a network operator can lock a mobile device to its network. The mobile device obtains the SIM lock-related parameters that enable the mobile device to operate in the network from the SIM card via a card reader in the mobile device.
The current electrical interface (standard) that describes how SIM cards and their associated card readers should function realizes an open physical channel between the SIM card and the card reader in the mobile device that is unprotected. As a result, the interface is susceptible to being penetrated by an active wiretapper. Attacks that have been reported, for example, include those that “spoof” the SIM lock system by inserting a micro chip between the electrical interface of the SIM card and the SIM card reader in the mobile device. The micro chip provides bogus data when the mobile device requests the SIM lock-related parameters from the SIM card, and can enable unauthorized use of the mobile device.
Even an authorized user of a mobile device may find it advantageous to function as an active wiretapper in certain situations. For example, a user may obtain a subsidized mobile phone from one network operator in return for agreeing to utilize that operator's network. The user can then actively wiretap the open channel between the phone and the SIM card to enable the user to use the phone in another network. As a result, the operator that provided the subsidized phone to the user can lose its investment in the subsidized phone.